Even when communication apparatuses participating in a network are added or removed, an ad hoc network is dynamically formed and thus is highly convenient. Therefore, the ad hoc network may be applied to a sensor network. However, after the ad hoc network is formed, information is transmitted to all the communication apparatuses participating in the ad hoc network in some cases such as when program files used in the communication apparatus are updated or when a setting is changed. In this case, the updated program and information such as a setting value are downloaded to a communication apparatus operating as a gateway in the ad hoc network. In the following description, the communication apparatus operating as the gateway in the ad hoc network is simply described as a “gateway”. The gateway broadcasts the downloaded information. Further, the communication apparatus which has received a broadcast frame broadcasts a frame including information which is included in the received broadcast frame.
As a related technology, a broadcast communication system has been proposed which re-transmits a frame only when a predetermined number of a negative acknowledgement is received for one or more data frames.
Japanese National Publication of International Patent Application No. 2004-535124 is an example of a related technology.
As has been described as the background art, if the information that the gateway has downloaded is broadcast, a communication apparatus which receives a broadcast frame also performs broadcast, such that the number of frames which are transmitted and received over a network becomes enormous. Therefore, if information is attempted to be transmitted to all communication apparatuses in a network by a broadcast, congestion is likely to occur in the network. Further, if broadcast is attempted to be performed frequently so that congestion does not occur, the transmission interval of the frame is increased, and thus it takes a long time until the data pieces reach all the communication apparatuses in an ad hoc network.
Even if the retransmission method described as the related technology is applied, it is not possible to avoid the occurrence of congestion in a network due to frames other than a re-transmission frame. Further, since the communication apparatus which receives the broadcast frame does not transmit an acknowledgment to a source, the system which has been described as the related technology is not applied to broadcast transmission in the ad hoc network.
An object of embodiments is to provide a communication method of suppressing the occurrence of congestion in the network.